Free piston combustion engine



Feb; 12, 1952 c. B. BRlGHT FREE PISTON COMBUSTION ENGINE 3 Sheets-Sheet1 Original Filed May 8, 1946 Feb. 12, 1952 c. B. BRIGHT 2,584,981

FREE PISTON COMBUSTION ENGINE Original Filed May 8, 1946 3 Sheets-Sheet2 7 105 I /0/ Kg .1

Feb. 12, 1952 I c, a BRIGHT 2,584,981

FREE PISTON COMBUSTION ENGINE Original Fi led May 8, 1946 3 Sheets-Sheet5 Patented Feb. 12, 1952 5 .a 1,.1. in

I QEFICE- (Granted under act of .March 3,1883, as

a r amended April 530,

This invention relates to power plants of generalutility andparticularly to those of the "type -in'which intermittent energy ofanexpandable 'gas is transformed into useful work ata desired rate.Briefly, the system comprises 'an expandable gas engine, a liquidpump'drivenbythe'em gine," a reservoir for receiving the liquidund'erpressure, a motor driven by the high.'pressure liquid, and suitablemeans for automatically'startingthe engine or operating it during thenonworkingportion of its cycle of operation.

An object of the invention is the provision of a power plant, whichintermittently receives energy inone portion "thereof; and either-storesthis energy'for subsequent use in the form "of'potential energy ofaliquid under pressure-or trans- -forms the intermittent energy into'-usefu1 u'r'ork at a'constant or other desired rate. Y Another objectis-the provision of a power plant which includes a-motor for doing workat arsesired' rate coordinated with"an e'ngirie-in such manner that theengine automatically supplies ;the motorwith energy maccordance with thepower requirements thereof! Another object isltheprovision of a powerplant .which .has' a motor capable of delivering run torque whenstarting,'coordinatedwith a coin- .bustion engine for drivingsame"whioh"autoinatically'starts simultaneously withthe inctorx' Anotherobject .is the provision of a combustion'iengine twhich utilizesstoredenergy-ofa liquid under pressure 1 to automatically recharge a vcombustion chamber in event: of a misfire'; Another .object is, toachieve. high thermal efii- .ciencybythe provision of an expandablegasien-i ginewhichis capable of operating on a cycle lsuchthat exhaustpressures are at an optimum lowvalue, despite high resistingforcestendingtto stopothe engine. 1,

Another objectis theprovision of a liquid cir- .culatory ,system inwhich. the. liquid. may. be em- .p10yed'..to .operateamotoror ini anyother system which requires a differential head onthe. liquid. Furtherobjects are .the provision of a power .plant which has a minimum numberof parts all ofwhich are readily accessible; has :high:power :outputperunit jof weight,.is SllbjECtQtO' aiwide variation of. arrangements,of its componentmarts, .and, has. inherent cushioning .feat'ureslf or.the;.ex pandingiorces of a gas. r 1 Still'further objects, advantages,and salient .lfeatures' will becomeapparentifrom 'a" considera- Lt'ionof .the description toifollowgthe accompanying drawings, 1 and theappended 'claimsf E 1.This;application\ is andivisien ofi'iapplication'Serial No. 668,054,- filed'May 8, 1946, for Hyrdaulic --.'Power--Plant."

w -Ir'ithe drawings: I 'Fig. i1"is a 'side'view, partly in section, of ade- 5 viceemb'odyin'g my'invention; r v r Fig.2 is a detail 'ofFig. 1;

' Fig.3 is'another detail of Fig. 1; :F'igirlisan alternate constructionof a portion of the bell crank linkage of .Fig. 1; shown in: one

position j;

Fig. :5 is a view similar to Fig. linkage in' anotherposition; Fig-Bis aview of an alternate turbine control mechanism; ':":.Fig'.f'7 is anotheralternate construction of a portion ofthe bell crank linkage of Fig. 1,shown one position; and y .Fig. 8 is a view similar tojig. 17 showingthe =linkagein another position. i f p Referringtothe drawings, agenerally cylindrical support ID forthe various parts of the deviceisrecessed atthe .topvfor the reception of an ex- :ipandablegas primemover, shown inithe form of .anair-rcooled; two-cycle internalcombustion en- .25Jgine cylinder, vhaving a conventional piston 12,"exhaust .,port 13, intake port 14, compression 'IChfllIlbQl'ilfi, sparkplug 16 and carburetoriconnectioIiJlJ. v.To promote clearness in'the.drawings, ...the ignition system including batteries, coils, contactzpoints, -etc., are not shown, but it ,will be ."understoodthat anyconventional system which would effect ignition at a predetermined pointin .theitrav el ofpiston l2 couldbe employed. The .1carburetcr, also notshowmcmfld b o a y 9 -ventional tyne. I

. :On the opposite side, andwithin the confines of support In, islocated a liquidpump; illustrated as aipist .lfirecip ocabl gina cliuderfl- T .pistcnis on ra l qnnected orist nfibxmean .of connectin jqd.20, .b ll cr nks? .l n 2 a ,pistQnxQd-H- Al s p tessu e l q es rro l -lan l w pressur l ui rese voi 1 am .proy ded ith supp r i0 a d. i c mmnica i .w t h .se r irs atio e e d o t np9rt is .a rev rsi l iliquid.turbi .145 cjons cte ..t ,on -.f '9 n t liquid in; reseryoir'le and thusdrive sliaft' .2;1oto 'which may .be coupled any sort of power drivendevice; The turbine; tobe subsequently described 50- ingreateradetailgisof the type wherein the delivered power is determined. by the,amount'of; liquid x'fiow;therethrough, which in turnis determined bythe setting of. the adjustable turbine blades 28. -.The liquidafterpassingfthrough theturbine en- 56 ;ters;low1pressure reservoir ;25and is then re- .4 showing the turned to high pressure reservoir 24 bypiston I8 part or all of the intermittent energy imparted to the liquidin reservoir 24 may be stored for subsequent use. The volume of, air in'tank 32 should be sufficient to ensure as little fluctuation ofpressure as possible so that the liquid in reservoir 24 remains undersubstantially constant pressure regardless of its change in volume. Thisis desired to provide a smooth flow of power from the turbine. Bellows3I also serves the. purpose of dividing the air and liquid into separatecompartments and hence eliminates emulsification of the liquid or theentrainment of air bubbles therein, which are both objectionable. It isnecessary that the'low pressure reservoir 25 be of variable volume,also, to accommodate any excess liquid delivered thereto by turbine 26and which is not directed immediately to pump piston I8, and to this enda bellows 33 is provided in a.

wall of reservoir 25.: This bellows is urged in one direction by aspring so that the liquid received in reservoir 25 will always besufficient for the requirements of pump pistonIB.

It is apparent that since no flywheel is employed to return piston I2 tothe end of itscompression stroke for a. subsequent power stroke, somemeans are necessary to perform this function, and to this end a plunger35 attached to piston I8 and extending into reservoir 24 is pro-. vided.At the end of the power stroke, a portion of the energy stored in theliquid in reservoir 24 is utilized to force plunger 35. and the linkageconnected between same and piston I2 to return the latter to the end ofits compression stroke at which point ignition occurs and the cycle isrepeated. Thus, the liquid in reservoir 24 is analogous to theconventional flywheel but has the advantage that operation of the systemdoes not depend upon heavy and cumbersome inertia parts, and further,does not require continuous operation as in the case of a flywheel;thatis, energy can be stored in reservoir 24 and later used to rechargethe engine when it becomes necessary, rather than continuously rechargesame as would result if a flywheel were used. It becomes apparent,accordingly, that as the power requirements of shaft 21 vary, cylinderII automatically supplies these power requirements by varying its rateof operation and hence the.

amount of liquid circulated through the system previously described.

The normal operation of the parts so far described is summarized asfollows, it being assumed that the turbine vanes 28 are open to theextent.

of the power required, piston I2 is at the'end 'of its stroke, as shown,and a combustible charge has been transferred from compression chamber Ito the combustion cylinder: Liquid under pressure in high pressurereservoir 24 forces" plunger 35 outwardly which in turn through pistonI8, piston rod 20, linkage 2|, 22, and 23 forces piston I2 to the end ofthe compression stroke as shown by the broken line in cylinder II. A newcombustible charge enters com-' pression chamber I5 through carburetorconnection H as a result of inward movement of piston I2. At the end ofthe compression stroke ignition occurs forcing piston I2 outwardlycompressing the mixture in chamber I5 andat approximately the positionshown products of combustion exhaust through port I3, and the compressedmixture is transferred to the cylinder through port I4 at which time thecycle is completed. During this cycle piston I8 has transferred liquidfrom low pressure reservoir 25 to high pressure reservoir 24 from whichit passes through the turbine to do useful work. While "piston I8delivers energy to reservoir 24 interstopping and starting of the systemis automatic which isv summarized as follows, it being assumed that theturbine blades are closed to preclude liquid flow therethrough: Liquidin high pressure reservoir tends to move plunger outwardly as beforedescribed, but since the turbine is not discharging liquid into lowpressure reservoir 25, piston I8 tends to create a partial vacuum inreservoir 25 which will restrain outward movement of piston I8 sinceatmospheric pressure acts on the outer side thereof. Thus, the entiresystem stops automatically. When the turbine blades are again opened toresume operation. liquid again flows through the turbine and intoreservoir 25 and cylinder I9. The partial vacuum therefore no longerexists which permits plunger 35 to again force piston I2 to the end ofits compression stroke as explained under normal operation.

From the foregoing it is apparent that under conditions where the poweroutput of turbine 26 remains substantially constant, piston .I2 willautomatically operate on a conventional twostroke Otto cycle; however,under certain conditions, for example, when a misfire occurs by reasonof faulty ignition, or where the mixture in the power cylinder hascondensed because the system has been shut down, it becomes necessary tocondition the engine for a subsequent power stroke. To this end. aself-starting device is provided. This device comprises a cylinder 4Ihaving a plunger 42 therein which is connected to hell crank 2| by link43 and pin and slot connection 44. With the leverage relationships asshown, it would be necessary to construct plunger 42 with a greatercross-sectional area than plunger 35 since the former must overcome theresistance of the latter. Should a misfire occur and hence insufiicientcombustion pressure exist to return piston I2 on a power stroke, plunger35 would move piston I2 beyond the normal point of travel where ignitionwould occur. This increase in travel would bring the pin in link 43 tothe bottom of slot 44 and hence plunger 42 "of spring 48.

'moves hydraulic actuators 5I and 52 downwardly. Hydraulic actuator 52through the medium of the liquid in line 53 actuates plunger 54 openingvalve 29 which permits liquid trapped in pump cylinder I9 to be returnedto storage reservoir 25. Simultaneously with the foregoing, hydraulicactuator 5I through the medium of the liquid therenular pace 85 andthence to reservoir '25. y Y ensure against loss of pressurein'reservoir 24 below-moves plunger 55 to the left, opening threeway:valve 56 against-{the urge of compression spring 51. This permits flowof high pressure liquid into cylinder M by ,way of pipes 58 and 58operation. Also, at this point, pin 46 is moved to the position shown at46c releasing 'crosspin 48 from beneath lever -58. This allows spring.51 to urge three-way valve 56 to its normal position where the liquidin 41 is in communication with .low pressure reservoir 25 by way ofconduits 5,8 and 68. As piston I2 movestoward the end .of thecompression stroke, plunger 42 and cam I5 movetherewith, and pin 46 ismoved to its original position at 46a with crosspin 48 againrepositioned below lever'58 torepeatthe foregoing starting operationwhen it again becomes necessary. When piston I2 is normally functioningon its power and recharge strokes, link 43 merely swings back and forthwith one end riding in pin and slot connection 44, plunger 42 remainingstationary. A check valve 6I may be provided in line 68 to preventpressure fluctuations in reservoir 25 from effecting operation of plung-The reversible turbine 26, previously mentioned, comprises a hub 88mounted on shaft 21 and carries on the periphery thereof a plurality ofvariable pitch vanes 28. These vanes maybe constructed to provide afluid seal between their inner edges and the hub, between their outeredges and casing '8I in which they rotate, and

between their radial edges so that when the vanes are in closedposition, they act as a valve to prevent fiow of liquid through theturbine. The

pitch of the blades is controlled by a slidable control collar 82 whichhas a cam slot 83 therethe other from a position in which the blades areclosed will adjust the pitch of the blades in either of two directionsso that the turbine will rotate either in a forward or reversedirection; The amount of power desired at shaft 21 1s controlled bythebladepitch,'an increase thereof permitting greater flow of liquid andhence greater power, and a decrease thereof decreasing the power. Liquidexhausted by the turbinefiows-into' andue to possible leaks in turbine28 when the unit is shut down, a valve 86 may be provided. Under someconditions of control, it may be'found desirable to regulatethe powerrequirements by valve 86 also; thus, for example,-fixed pitch turbineblades could be provided and-the flow theretothrottled by valve 86.

In some instances, it will be desirable to construct, air tank82 ofrelatively small size in which case it would not be capable ofmaintaining constant pressure on the liquid in reservoiri i, as

previously explained. In this event, a control as shown in Fig. 6 may beprovided to eliminate fluctuations in power of the turbine which wouldresult from fluctuations of liquid pressure in reservoir24. In-thismodification a lever' 8I is pro- ,vided,,one end of which maybe lockedat-various positions in notches alongquadrant 82 but free to pivotthereabout. The other endof lever 8| is connected :to collar 82 by yokeand pivot 83. A bell crank 94 has one end thereof connected to lever 8Iby pivot 85 and the other end to a link 86. Link 86 is connected tooneendof lever .91 which is pivoted at-its center 98. A slot 88 is providedin lever 91 extending on both sides of the centerthereof, and a link I88has one end slidably engaged'therein. The opposite end of this link isconnected to rod I8I which is connected to bellows I82, the outside ofwhich is in fluid communication with reservoir .24. A suitablecompression spring I83 urges the bellows 1I82 to the right. Link I88would remain'in the position shown under the urge of spring I04 when theunit is not in operation and in either position I85 or I86 when inoperation, one position corresponding to a forward direction of turbinerotation and the other to a reverse direction of rota.- tionh Assumingthat the turbine blades are open to effect forward rotation and thatlink I88 :is in the position shown at I85, an increase in liquidpressure on bellows I82 correspondingto a sudden pulsation would rotatebell crank 81 clock- Wise, which through link 96 and bell crank 84 wouldmove control collar 82 toward-its neutral or off position. This wouldreduce the turbine blade pitch, restrict liquid flow through th turbineand henc prevent the sudden increase in liquid pressure from efiecting.the smooth fiow of power from shaft 21. Conversely, if the-turbine isoperating in reverse, link I88 would be positioned as shown at I86, andcollar 82 would be positioned to reverse the blades as previouslydescribed. An increase in pressure on bellows I82 would move bell crank81 counterclockwis and through link- 86 and bell crank 84 again forcecollar 82 toward its neutral or oil position thus compensating for thefluctuation as described for forward operation. It is apparent thatwhile the foregoing has been describedfor an increase in pressureinreservoir 24, a decrease in pressure would cause the oppositeefiect.that is, a decrease would tend to open the turbine blades for momentarydelivery of more liquid therethrough. To place link I88 in position I85or I86, apair of solenoids I81 and I88 are provided which are connectedto suitable switches-I88 and I"I8 on control quadrant 82. When-lever 8|is initially moved from its oil position to either forward or-reverse,-it completes a circuit to one or the other andspring-IMinstantly returns link-l88 to the position shown. Thus, if'an explosionshould occur in cylinder II after the solenoid circuits are broken, theincreaseof liquid pressure resulting therefrom would not effect changeof turbine blade pitchsince link I88 would previously have been moved toan inoperabl position by spring I84. If for any reason-itisdesired torender the positioning, means inoperative, switch I II may be left open.Also, when the arrangement for damping fluctuationis notemployed,lever,8l may be the sole control, pivot 85 in this cas beinga'fixed pivot and the remainderof' the l nkage-connectedtheretoliminated. 1

F e: l'i e cr k ,2 isi lus atedas a simple lever pivoted intermediateits ends to promote 7 clearness to the drawings. It is contemplated,however, that the lever 2| of Fig. 1 and its associated linkage may takethe form as shown in Figs. 4 and 5 in which corresponding parts areindicated by primed reference characters. Bell crank 2I' is grooved atID to receive a pin II which is slidable therein and also in anothergroove I2 in frame member 13. Link I4 connects pin 'II to pin I5 onconnecting rod 20. Connecting rod 20' is pivotally connected to bellcrank 2I' by pin I6. From Fig. 5 it can be seen that as piston rod 23moves outwardly on the power stroke of piston I2, pin II slides ingrooves I and I2 changing the mechanical advantage of the lever arm of2I in favor of piston I2. Despite the decreasing pressures resultingfrom the expanding gases, this permits piston I2 to overcome theresistance of pump piston I8 which operates against substantiallyconstant back pressure. It is thus possible to carry expansion incylinder II to a point where optimum thermal efliciency may be obtaineddespitev the constant resisting force against pump piston I8, thusincreasing the overall efficiency of the entire power plant. .It is tobe observed, also, that on the compression stroke of piston I2 themechanical advantage constantly increases infavor of the connecting rod20 which is operated by plunger 35, and hence the increasing pressuresof compression can be overcome thereby. In operation of the foregoingarrangement, the amount of fuel metered to the combustion chamber may beso regulated that the pressure of the expanding gases in the cylinder atany point of the expansion stroke will be just sufficient to overcomethe back pressure exerted on pump piston I8 by the liquid in reservoir24. The engine in this case would operate on a substantially true Ottocycle. If it is desired to increase the power output per stroke ofpiston I2, still retainin operation on a substantially true Otto cycle,the pressure in tank 32 may be increased, effecting a higher backpressure against which piston IB must operate and increasing the amountof fuel delivered to the cylinder I2 per stroke to provide increasedcombustion and expansion pressures to overcome the higher back pressureon piston I8.

Figs. 7 and 8 show an alternate form of the linkage shown in Figs. 4 and5, this modification permitting operatidn of the engine on a modifiedOtto cycle. The linkage is all identical to that of Figs. 4 and exceptthat link 14 is constructed in two parts 14a and 14b, connected bypivotal connection 14c, the two parts having limited pivotal movementbetween stops 14d and Me. This latter linkage permits a delayed or lostmotion connection between piston I2 and the fulcrum changing mechanism,that is, piston I2 may move part way out on its expansion stroke withoutchanging the mechanical advantage in its favor but after reaching apredetermined point the fulcrum changing mechanism becomes operative,and the leverage increases in favor of piston I2 for the remainder ofthe stroke. Fig. '7 illustrates the position of the parts at thebeginning of the expansion stroke with links 14a and 14b in onerelationship. the distance between pins 15 and I I being at a minimum.Fig. 8 illustrates the position of links 14a and 14?) at the pointcorresponding to a predetermined position of piston I2 where theleverage in favor of piston I2 has commenced. Links'I Ia and MD are nowin their extended position with the distance between pins I5 and II at amaximum. Furthermovementof leverage in favor of piston I2 in the sameman- 'ner as described for the linkage of Figs. 4 and 5.

With this arrangement, it is possible to modify the true Otto cycleslightly which is effected as follows: Assuming that the pump piston I8is operating against the same back pressure as the modification of Figs.4 and 5 and a larger amount of fuel is introduced into the powercylinder by opening the carburetor throttle valve, then the compressionpressure would be higher and hence the peak pressure following ignitionwould tend to rise beyond that of the embodiment of Figs. 4 and 5. Sincethis pressure would be in excess of that required to overcome theresistance of pump piston I8 and since piston I2 is a free piston, themovement of which is determined by the difference between the forces ofcombustion and the resisting forces, it will tend to move outwardly sothat the peak pressure above referred to would not be reached. Theinitial part of the expansion stroke would therefore approach a constantpressure curve, that is, a line parallel to the volume line on apressure-volume indicator .card. This pressure being constant, noincrease in leverage in favor of piston I2 would be necessary until thepressure began to fall. At this 7 point, the linkage Ha, 14b would havereached a point where the leverage in favor of piston I2 would commenceand as the expansion pressures decrease on a curve simulating theexpansion curve of an Otto cycle, the decreasing pressure would still becapable of overcoming the resistance of pump piston I8. It will beobserved also that on the compression stroke, initial outward movementof pump piston I8 will first move links 14a, 14b to their relativeposition as shown in Fig. '7; further movement will then move pin 'IIupwardly in slot 12 increasing the lever arm in favor of pump piston I8so that as piston I2 approaches the end of its compression stroke,sufilcient force is available to overcome the compression pressure.

In event that reservoir 24 is filled to capacity this would precludestarting of the system, whereas if no high pressure liquid remains inreservoir 24, starting may be effected by auxiliary pump 11 which willtransfer liquid from reservoir 25 to reservoir 24 and thus establishsuflicient reserve energy in reservoir 24 to start the device in thenormal manner previously described. It is apparent that the drive meansfor such pump may take any suitable form consistant with therequirements of the system as a whole. One example would be an electricmotor.

The various parts of the device would, in perhaps most cases, be sodesigned and proportioned relative to one another to give optimumoverall efliciency and in this connection, it should be observed that ifa certain air pressure in tank 32 is chosen and also a fixed throttlesetting in the carburetor, the engine will always operate onsubstantially the same thermodynamic cycle, and variations in powerrequirements of the turbine will change only the rate of such cycle;that is, for example, an increase in power requirements automaticallyeffects more power strokes per unit of time by the engine, but itsactual thermodynamic cycle remains substantially unchanged. Theconventional engine, on the other hand, varies its thermodynamic cycleunder change of load, and usually at full load the cycle is leastefficient thermally. The advantages of this type of engine thereforebecome readily apparent since in this invention an optimum efficientthermo- 9 dynamic cycle can be chosen which will remain the same undervariation of load. c Q

In some cases it may be desired to change the potential power output ofthe system, either by loading it over a designed optimum load ordecreasing its loading from a designed optimum loading. Thethermodynamic cycle attendent with such changes can be chosen in asimple manner by this invention. If a higher output is desired, forexample, a greater air pressure is employed in air tank 32 by admittingair through valve 18. This, in turn, calls for a higher output by pistoni2 so the carburetor throttle is merely opened in acordance with theincreased power requirements. Similarly, if it is desired to reduce thepotential power output, the air pressure is decreased and the throttlevalve closed somewhat from its normal designed position.

While the previous description sets forth the expedience of theinvention as a meansto obtain uniform power from an intermittent powersource, and especially one having a minimum number of working'cylinders,it is to be observed that the device has" equal application toinstallationswhere intermittent power is desired. The reserve energy inreservoir 24 is instantly available for requirements of the turbinewhether they be continuous, variable, or intermittent power, it onlybeing necessary to adjust the turbine blades in accordance with thepower needs of shaft 21, and the remainder of the system automaticallysupplies these requirements.

It is apparent that while several specific embodiments of the inventionhave been described, this is intended only for purposes of teaching theprinciples of the invention rather than as a limitation thereon. Theengine, for example, has been described as a two-cycle, air-cooled Ottotype, but it is apparent that it could be liquid cooled or operated onother cycles such as the diesel cycle wherein a fuel injector would besubstituted for a spark plug and ignition would take place as a resultof the heat of compression. Steam or other gases could also be employedas the expansible medium if so desired, the only requirement being thatsuitable valves would be incorporated to control entry and. exhaust ofthe gas. The expandable bellows for effecting variable volume of thereservoirs could be in the form of pistons slidable in cylinders againstthe urge of suitable springs, and the turbine is subject to widevariations in its form. The various components, while illustrated incompact arrangement could be located in other suitable relationshipsdepending on the installation requirements of the power plant.Similarly, the starting mechanism could be controled by sundry meanssuch as solenoid operated valves as will become aparent once the broadteachings of the invention are understood.

Further, the device, while disclosed as a system in which power isdelivered to a shaft, could well function as a pumping device by merelyeliminating the turbine and incorporating the remainder of the device ina fluid system which requires for its operation the movement of a liquidat a continuous rate, a variable rate, or an intermittent ratein eithera closed or open circuit. Thus, as a pump means in a closed circuit, theinvention could be employed with any device which requires for itsoperation a flow of liquid under differential pressure; in an opencircuit, it could receive liquid from any source of supply and deliver acolumn of liquid to efiect useful work. As an example of the latter, the

10 invention. could. be employedfor hydropropul'si'on.

It is' accordingly'intended that the claims to follow should beconstrued in terms of the broad teachings above set forth and not aslimited to the exact embodiments illustrated.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

1. An engine having a piston movable between anoutward limit ononestroke and'ia normal inwardlimit on its return stroke, the normalinward, limit being determined by a predetermined gas pressure acting onthe piston at such limit, first means for moving the piston through itsreturn I'stroke to thenormallimitaforesaid and also capable of movingthe piston beyond such. limit inevent that the gas pressure is less thanthe predetermined amount, and second means" responsive to movement ofthe piston beyond the normal inward movement to return the piston to itsouter limit.v

.2. An engine having a piston movable between an outerward limit on itspower stroke and a normal inward limit on its compression stroke, thenormal inward limit being determined by the ignition of combustiblegases, a first means for automatically moving the piston through itscompression stroke to the normal limit aforesaid and also capable ofmoving the piston beyond such limit to automatically return the pistonto its outer limit for subsequent operation of said first means wherebythe piston is automatically moved back and forth in event of a misfire:

3. A device for actuating a piston through one direction of itsreciprocating movement comprising; a plunger directly operable from asource of liquid under pressure, linkage means operably connecting saidplunger to the piston, a cam operable by said plunger, and valve meansoperable in response to movement of said cam for controlling the supplyof pressure liquid to said plunger.

4. A device for actuating a piston through one direction of itsreciprocating movement comprising; a plunger operable from a source ofliquid under pressure, linkage means connecting said plunger to thepiston and including a pin and slot connection which effects no movementof said plunger when the piston moves to a predetermined point buteffective to move said plunger upon movement beyond said point, a cammovable by said plunger, and valve means operable in response tomovement of said cam to deliver the liquid under pressure to saidplunger.

5. An internal combustion engine comprising a power piston having acompression stroke and an expansion stroke, a fluid motor mechanicallyconnected to said power piston to move it through its compressionstroke, a second fluid motor mechanically connected to said power pistonto move it through its expansion stroke, and means responsive to amisfire at the end of the compression stroke of said power piston forcontrolling the operation of said second fluid motor.

6. An internal combustion engine as defined in claim 5 wherein saidconnection between said fluid motor and said power piston comprises alever oscillated by said power piston, and a toggle linkage between saidfluid motor and said lever connected through a pin and slot connectionto allow said motor to remain inoperative during normal operation ofsaid power piston, and to provide positive movement of said piston onits expansion stroke during motor operation.

7. An internal combustion engine as defined in claim 6, wherein saidsecond fluid motor control means comprises a cam means and control valveoperated thereby to start said motor, said cam means being operated inresponse to movement of said power piston beyond the end of its normalcompression stroke as a result of a misfire, said cam means beingconnected to said motor for return to its original position at the endof the normal compression stroke of said power piston.

8. A device for actuating a piston through one direction of areciprocating movement comprising, a plunger operable from a source ofliquid under pressure, means connecting said plunger to the piston, acam, said cam being inactive during the first portion of a piston strokein one direction, means interconnecting the plunger and cam to move thecam near the end of said stroke, and valve means operable in response tothe cam movement for controlling the flow of the pressure liquid to saidplunger whereby the plunger will move the piston on its return stroke.

9. A device for actuating a piston through one direction of areciprocating movement comprising, a normally stationary plunger, 9.source of liquid under pressure, means for connecting said plunger tothe piston and means for operatively connecting said plunger to thepiston during the last portion of an abnormally long stroke of thepiston to move the plunger, a cam operable by said movement of theplunger, and valve means operable in response to the cam movement forcontrolling the flow of pressure liquid to said plunger whereby theplunger will move the piston on its return stroke.

COOPER, BUCK BRIGHT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

